The present invention relates to an electromagnetic braking apparatus for controlling molten steel flowing down in a casting mold by applying an electrostatic magnetic field to the molten steel supplied from a submerged nozzle into the casting mold, in the continuous casting of the molten steel.
A method of controlling molten steel flowing down in a casting mold by applying an electrostatic magnetic field to the molten steel supplied into the casting mold is effective to gather and catch inclusions and prevent the entrapment of powders and bubbles when killed steel and in particular low carbon Al killed steel is continuously cast at a high speed.
Electromagnetic braking apparatuses used to this method are disclosed in Japanese Patent Examined Publication No. 2-20349 and Japanese Patent Unexamined Publication No. 2-284750 and generally have the arrangement shown in FIGS. 1 and 2. A casting mold 1 with a rectangular cross section has wide side walls 2 and narrow end walls 3. An electromagnet 10 is disposed along each of the side walls 2 and has a core 7 and coil 8 wound around the core 7. A magnetic path forming iron core 13 is connected to ends of the cores 7 and extends to surround the casting mold 1 to thereby constitute an electromagnet device for applying an electrostatic magnetic field in the direction across the side walls 2 of the casting mold 1. The electromagnet device is mounted on the support frame 6 disposed on a vibration table 9. The support frame 6 further supports a cooling box 5 for cooling the casting mold 1 and width changing device 4 for changing the width of the casting mold by moving the end walls 3 of the casting mold. The magnetic path forming iron core 13 has a reduced thickness at the portion thereof to be interfered with the width changing device 4 and support frame 6 to prevent the interference with these components. Further, the corner of the magnetic path forming iron core 13 is chamfered to prevent the interference with water pipes 11 connected to the cooling boxes. Further, an opening, through which the magnetic path forming iron core 13 passes, is defined to the cooling box so that the magnetic path forming iron core 13 extends to surround the casting mold and the electromagnet.
The electromagnet device must reduce the magnetic resistance of the magnet path forming iron core to effectively produce an electrostatic magnetic field. For this purpose, the magnetic path forming iron core preferably has a large cross sectional area. Nevertheless, since the magnetic path forming iron core of the conventional electromagnetic braking apparatuses has a portion with a reduced cross sectional area to prevent the interference with other components such as the support frame, width changing device, duct and the like, the electromagnetic braking apparatus cannot produce a magnetic flux density of about 2000-5000 Gauss at the center of the casting mold. Further, when an electromagnetic device capable of producing the above magnetic flux density is provided by using an magnetic path forming iron core having a portion with a reduced cross sectional area, the weight of the magnetic path forming iron core is increased and thus the size of a support frame for supporting it is also increased. Further, a crane associated with a vibration device and continuous casting mold and a motor for the vibration device must has an increased capacity. Furthermore, another problem arises in that since the large magnetic path forming iron core extends through a cooling box, the flow of a coolant in the cooling box is obstructed.
Therefore, an object of the present invention is to provide an electromagnetic braking apparatus for a continuous casting mold capable of producing a magnetic flux density of about 2000-5000 Gauss at the center of the casting mold without increasing the weight of the continuous casting mold.